The present invention relates to improvement in stave cooling devices for metallurgical furnaces such as blast furnaces, and more particularly the invention relates to an improved stave cooling device so designed that a crack produced in the stave main body by the heat load from a furnace is prevented from extending to the cooling tube portion and causing a total failure of the device.
Generally, the hearth walls of a metallurgical furnace such as a blast furnace are constructed of refractory bricks and suitable cooling boxes are installed everywhere through the outer shell. However, as the result of the recent trend toward larger blast furnaces, the heat capacity of hearth has been increased very greatly and the cooling capacity of the cooling boxes has been found insufficient for the purpose. Thus, practically all of the recently installed blast furnaces are equipped with stave cooling devices. As regards the utility of such stave cooling device, on the one hand the device must of course be excellent in heat resisting and abrasion resisting properties and capable of firmly sustaining the hearth wall over a long period of time, and on the other hand the device must meet the optimum conditions with respect to the effective heat exchange at the hearth-side heat receiving surface of the stave, the heat transfer efficiency between the internal cooling pipe line and the stave main body, the prevention of a crack produced in the stave main body from extending to the cooling pipe line and so on and its manufacturing process must also be simple.
Stave cooling devices proposed in the past include a so-called unwelded type in which the cooling tube is of the single-tube type and the tube and the stave main body are not welded together, a double-tube welded type, etc., and the method for preventing the cooling tube and the stave main body from being welded together mostly consists of applying a non-metallic coating to the surface of the cooling tube and then cast-mounting the cooling tube in the stave main body.
However, the stave cooling devices which have heretofore been put in practice and used are disadvantageous in that they are incapable of giving a full play to their valuable utility due to the inferior efficiency of heat transfer between the cooling tube and the stave main body with the resulting melting loss of the main body and due to the fact that a crack produced in the stave main body tends to extend to the cooling tube due to an insufficient welding preventing treatment and so on.